In a wireless communication system in which communication is performed by mobile stations via base stations, in order to maintain a predetermined communication quality, there is a related technology in which a base station sends and receives a signal to and from a mobile station by cooperating with a peripheral base station that is other than the base station. In this wireless communication system, first, a mobile station receives a signal from a base station that is currently performing communication (hereinafter, referred to as a “serving base station”) and a peripheral base station and then measures, from the received power, the signal-to-interference ratio (SIR) thereof, which is the electrical power ratio between the serving base station and the peripheral base station. Then, based on the measurement result of the SIR, the mobile station selects a peripheral base station with which the serving base station is to cooperate. For example, when a mobile station selects a base station that has the maximum received power from among the peripheral base stations as the counterpart for cooperation, the mobile station sends a signal, to the serving base station, that requests cooperation with the selected base station. The serving base station that receives the request signal from the mobile station sends, to the selected peripheral base station, information needed for cooperation control. Consequently, a plurality of base stations cooperate with each other and thus communication is available with the mobile station.                Patent Document 1: Japanese Laid-open Patent Publication No. 2010-154262        Patent Document 2: Japanese Laid-open Patent Publication No. 2010-239417        Patent Document 3: Japanese Laid-open Patent Publication No. 2010-239303        Patent Document 4: Japanese Laid-open Patent Publication No. 2009-225137        
However, with the technology described above, because the cooperation control is led by a mobile station functioning as a terminal, there is, for example, the following problem. Even after the serving base station completes the scheduling of a mobile station accommodated in the serving base station's own cell, the serving base station, due to the occurrence of a cooperation request from the mobile station, needs to re-schedule by taking into consideration the effect on other mobile stations accommodated in the serving base station's own cell. Furthermore, when the peripheral base station is selected as the target for cooperation, because an additional request other than the scheduling to be performed for the selected peripheral base station occurs, there may sometimes be a case in which it is not possible to accurately obtain the channel quality or propagation loss in the uplink direction that is needed for the scheduling. In such a case, the mobile station is not able to accurately predict communication quality with each peripheral base station. Consequently, the mobile station may possibly select a peripheral base station that is not suitable for cooperation as the counterpart for cooperation with the serving base station. This prevents high-quality communication between the mobile station and the plurality of base stations.